Apparatus for forming finned tubing



Dec. 2, 1947.

G. E. CLIFFORD APPARATUS FOR FORMING FINNED TUBING Filed May 3, 1943 mmvma. szoass spun-0R0 n'r'rdnuevs Patented Dec. 2, 1947 APPARATUS FOR FORMING roman TUBING George E. Clifford, Detroit, Mich., assignor to Calumet and Hecla Consolidated Copper Company, Calumet, Micln, a corporation of Michigan Application May 3, 1943, Serial No. 485,512

2 Claims. (Cl. 80-2) The invention relates to the-manufacture of finned tubing of thecharacter described in the patents to Locke 1,761,733 of June 3, 1930, and 1,865,575 of July 5, 1932, and by the general type of apparatus disclosed in these patents.

obtain a product having a greater height of fin or peripheral diameter with respect to the diameter of the original tube than has heretofore been accomplished.

It is a further object to obtain a product in which the peripheral portions of the fins are free from cracks or other defects due to the circumferential expansion thereof.

Still'further it is an object to obtain a product which is in condition for further manipulation without any independent annealing step.

With these objects in view, the invention consists in the apparatus as hereinafter set forth.

In the drawings:

Fig. 1 is a side elevation, partly in section, illustrating an apparatus for carrying out my-improved method; and

Fig. 2 is a longitudinal section illustrating the successive steps in forming the fins together with the intermediate step of annealing metal.

Fig. 3 is a cross section on line 3-3, Fig. 1.

Generally described, the apparatus employed for forming the finned tubes, as illustrated and described in the patents above referred to, comprises a plurality of forming die rolls arranged about the periphery of the work and with their axes at av/predetermined angle to the axis of the work so as to simultaneously rotate and axially advance the latter. The die rolls are so fash- 5 It is the primary object of the invention to vancedthrough the apparatus and is discharged with the helical fins of full height formed thereon, said fins being free from any cracks or defects in the peripheral portions thereof. This is possible as the metal displaced by the first step to partially form the fins is annealed and softened before it is further operated upon by the successiveforming step. Consequently, the radial and circumferential expansion of the metal in thefinal step will not unduly stress the same.

More in detail and asillustrated in the drawings, A is a base or frame on which the various parts of the apparatus are mounted. B is one of the fin forming units comprising a plurality of forming rolls C, C' and D is a similar forming unit with forming rolls E,-E'. The units B and D are spaced from each other and between the same is arranged an annealing furnace F. This, as illustrated, is of the electrical induction type operated by high frequency alternating current which is passed through a helical conductor G surrounding the path of work. The tubing H to be finned. on a supporting mandrel I is advanced through the units B, F and D and is discharged with the helical fins fully formed thereon. If desired, it may be again annealed by passage through a furnace J similar to the furnace F.

Also, if desired, it may be cooled by passage ioned that at the point of initial engagement with the work they merely form a shallow narrow helical groove therein which, as the work advances, is widened to flow the metal axially between successive convolutions thereby forcing it radially outward to form the fin. The height of the fin is determined by the amount of metal that is displaced axially but, as this working of the metal has a hardening effect, there is a limit to the extent of radial expansion possible without rupturing the metal. With the present invention I have overcome this difficulty by effecting the fin formation in successive steps and interposing between these forming steps an annealing step.

In the apparatus the forming rolls for both steps are simultaneously operating upon the work during its axial advancement and in the space between the two sets of forming rolls there is arranged an annealing means. Consequently, the tube which is to be finned is continuously adthrough a cooler K before it is finally discharged. The object of the second annealing is to soften the metal so as to adapt it for further forming operations, such as, bending or coiling to fashion it for the particular apparatus for which it is intended. The units B and D are driven from roll heads L and M- containing suitable mechanism (not shown) and connected through shafts N and universal joints 0 to the forming rolls to be driven. The mechanisms within the heads L and M are driven in timed relation to each other by any suitable means diagrammatically indicated in Fig. 1 as a shaft T and gears T. I have also provided an auxiliary feed for advancing the tubing arranged between the unit D and annealing furnace F. This comprises a grooved roll P which is driven at an average peripheral speed corresponding to the axial advancement of the work through the medium of a variable speed successive steps in the forming of the finned tubing are'as illustrated in Fig. 2. The tubing H on where the induction heater G raises the temperature in the work to the desired point. It may not be necessary to heat the entire tube as it is only the fin or fin forming portions thereof that will be subjected to further manipulation. The work then passes into the unit D where the partially formed fins H are operated upon to reduce the thickness and increase the height thereof, as indicated at H. h

While I have described a process with only two successive fin forming steps, it is obvious that the number may be increased if it is desirable to still further increase the height of the fins. Also, while I have shown the annealing as effected by an induction type electric furnace, any other type of furnace or heating means may be substituted therefor whichv will heat the metal to the desired extent. Where electric heat is used, the degree of heating the fins or wall section is controllable by control of the heating ener y. To avoid oxidation or discoloring of the work during the annealing step, I preferably introduce a non-oxidizing atmosphere into the furnaces F and J. 7

While I have described the unit G for use in a position between two finning operations, it is possible that the second iinning unit M may at times be unnecessary, as for instance where a low height fin. is required. In this event, the

tube may be completely finned in one pass through unit B. The tube will then pass through deenergized helix G and through unit D with iinning rolls retracted or removed and will then be annealed and cooled, if annealing is required,

. 4 v I in units J and K. Such tubing will be applicable to bending or coiling work,

What I claim as my invention is:

1. An apparatus for forming, finned, tubing comprising a plurality of axially aligned spaced complementary partial fin forming units each including a plurality of fin forming rolls arranged about the periphery'of the work, an annealing furnace arranged between said units through which the work passes, means for driving said fin forming units in timed relation to each other, and an auxiliary means for advancing the tubing intermediate said units in timed relation to the advancement through said units.

2. An apparatus for forming finned tubing comprising a plurality of spaced complementary partial fin'forming units in axial alignment each including a plurality of fin forming rolls arranged about the periphery of the work, an annealing furnace arranged between said units through which the work passes, means for driving said fin forming units in timed relation to each other, and an auxiliary means for advancing the work intermediate saidunits comprising a grooved roll for engaging the work, a driving means and a variable speed transmission between said driving means and roll whereby the latter may be driven at the same peripheral speed as that imparted to the work by said forming units. I

' GEORGE E. CLIFFORD.

REFERENCES CITED The following references are of record in'the file of this patent:

UNITED STATES PATENTS Number Name Date 1,606,875 Heinauer Nov. 16, 1926 1,676,685 Cammen July 10, 1928 1,865,575 Locke July 5, 1932 

